Muffling device and method for internal combustion engine

ABSTRACT

A device and method for muffling the sound from an internal combustion engine is described, wherein the device is a tube made of a suitable material such as rubber and is attached to the exhaust outlet of the vehicle. Further described is a method of muffling the sound of an internal combustion engine that is comprised of taking a length of tubing having a spring disposed therein, and attaching one end of the tubing to the outlet of the exhaust of an internal combustion engine, and directing the other end of the tubing toward the ground surface, by forming an approximate ninety degree bend, such that the second end of the tubing is in close proximity with the ground surface, with the result that the sound level of the exhaust from the engine is substantially reduced.

PRIORITY CLAIM

The present application is a continuation-in-part application to non-provisional patent application Ser. No. 10/301,244, entitled “Muffling Device and Method for Internal Combustion Engine”, filed on Nov. 21, 2002, and claims priority thereto and the full benefit thereof.

TECHNICAL FIELD

The present invention relates generally to a device and method for reducing the exhaust noise of internal combustion engines, and more particularly to a method and apparatus for muffling the exhaust noise of vehicles, including particularly, but not limited to, four-stroke internal combustion engines.

BACKGROUND OF THE INVENTION

Beginning with the early days of internal combustion engines, there has been an effort to reduce the sound levels that are produced during operation of these devices. Typically, there are various sources of sound that are produced during operation. As the fuel/air mixture is detonated, there is the sound generated by the explosion. Internally, there are various moving parts that generate noise due to their interaction. During intake and exhaust, there is also the sound of fluid rushing in or rushing out of the engine.

While some of the noises emanate from the metal casing of the engine itself, a substantial portion of these sounds may be heard through the exhaust stream of the engine. Accordingly, efforts have taken place to muffle the sounds traveling out of the engine through this pathway.

Muffling devices have been developed with various methodologies for baffling the sound, thereby allowing the sound noise to dissipate, or to cancel itself out when sounds of opposite phase encounter each other. Mufflers are typically attached to all internal combustion engines that operate in public areas. Outside public areas, muffling has heretofore been of low priority, since the sounds have not been audible to a significant number of humans.

With growth of human population, and an increased amount of leisure time available, there are a larger number of people spending time in wilderness areas. Because the concentration of urban population has led to a substantial increase in the level of audible noise, efforts to prevent a similar increase in sound in suburban and wilderness areas have been made, with an increased focus on developing quieter machines for operation in such areas.

As sound waves spread out, their intensity decreases inversely with the square of the distance from their source. Thus there will be some attenuation due to this effect. However, the human ear does not respond linearly, so that doubling of sound intensity does not sound twice as loud to the human ear. For this reason, a logarithmic scale, or decibel scale, is used to measure sound pressure level with a typical minimum reference level of 2×10⁻⁵ N/m² at 1 kHz being equal to zero decibels, which is barely audible for a normal human hearing response.

The sound level can be determined using the formula 20 log p₀/p_(0t) dB, where Pot is the sound pressure at the threshold of hearing at 1 kHz, and p₀ is the sound pressure under measurement.

Thus, a sound of ten decibels is ten times louder, but 20 decibels is 100 times louder. For example, normal conversation is 60 decibels, while city traffic noise is in the 80-90 decibel range. While damage to the ear occurs with exposure to approximately 85 decibels or higher for long term periods, discomfort occurs at around 120 decibels, wherein mechanical damage to the ear occurs at approximately 160 decibels.

The present invention arose out of a need for a quieter All Terrain Vehicle (ATV). These vehicles are commonly used in off-road conditions, often in woods and other wilderness areas. To prevent disturbance to others, and in part to allow for a stealthy approach to wildlife, there is a recognized need to reduce the noise emissions of such vehicles.

The internal combustion engines of ATVs are usually four-stroke engines, otherwise known as Otto cycle engines. The present invention has been found to be particularly suited to reducing the sound noise of the emissions from such engines.

Manufacturers of vehicles, particularly ATVs, are required to meet certain limits on noise. It may be necessary for the manufacturer to limit horsepower of the engine in order to meet these decibel limits. Accordingly, it would be highly desirable for a manufacturer to be able to reduce decibels without sacrificing horsepower.

Although there are various engine muffling devices and methods available, each is disadvantageous when compared to the present invention.

For instance, U.S. Pat. No. 4,428,453 to Yuen et al. teaches a silencer device in which gases enter an upstream compartment of a silencer and flow through perforations in a tube and pipe into a chamber interior, then into an inverted trough through further perforations into a downstream compartment and an outlet. The foregoing describes a traditional muffler type device used on vehicles, and, while adequate for some uses, particularly in urban areas where there is much surrounding noise, it falls short in achieving a level of quietness desirable for wilderness areas.

U.S. Pat. No. 6,158,214 to Kempka et al. teaches a four-chamber type of construction for very small passenger transporting motor vehicles, wherein a silencer system partition divides the silencer into a 3-pot main chamber and an additional chamber (resonator). The Kempka et al. device is overly complicated as an add-on component to follow a standard muffler.

U.S. Pat. No. 6,382,347 to Gerber teaches a muffler device with a single inlet pipe and single outlet pipe having perforations in a portion of a pipe within a muffler chamber. While generally simple in design, the Gerber device still requires more components than desirable.

U.S. Pat. No. 4,848,513, issued Jul. 18, 1989 to Csaszar teaches “a compact noise abatement muffler for an internal combustion engine” wherein “exhaust gases passing through the muffler . . . achieve at least 4 changes of direction of gas flow”. While providing for a large reduction of about 10 decibels, the Csaszar patent requires complex construction in order to achieve four changes in direction of a gas flow.

U.S. Pat. No. 4,284,162, issued Aug. 18, 1981 to Ishida teaches a “tail pipe [that] is rendered considerably long to effectively silencing [sic] exhaust noise”. The Ishida patent discloses the use of a reverse bend to add length to the tailpipe of the exhaust. Furthermore, it provides a second length within a muffler body to add length to the path that exhaust must travel. Accordingly, the Ishida device requires several components, increasing the cost of manufacture.

U.S. Pat. No. 6,158,546, issued Dec. 12, 2000 to Hanson et al. teaches “an outlet tube with a funnel shaped element having a large diameter end positioned in an expansion chamber”. Further, Hanson et al. discloses a conical exhaust section, the conical opening being an internal component that opens up into a chamber within the exhaust system itself.

U.S. Pat. No. 5,214,253, issued May 25, 1993 to Houston, Jr. teaches “a flared expansion chamber”. The flaring of the expansion chamber in a single dimension requires the addition of a plurality of tail pipes, significantly adding to the cost to practice the Houston, Jr. invention.

Another possible method of sound reduction is the generation of vortices or eddy currents, which combine to cancel sound. U.S. Pat. No. 5,428,954, issued Jul. 4, 1995 to Cowan, Sr. teaches generation of “vortices effective to dampen exhaust noise vibrations and to contain the same as they dissipate into the atmosphere”. The Cowan, Sr. device is applicable to jet engines, where the exhaust is directed aftwardly, rather than towards the ground.

U.S. Pat. No. 4,220,219, issued Sep. 2, 1980 to Flugger teaches the “generation of sound dampening eddy currents in the chamber”, wherein “the generation of eddy current therebetween is preferably formed proximate the outlet tube of the muffler”. The Flugger requires that gas streams combine coming from opposing directions, thereby creating the eddy currents, and thus requires two exhaust sources, or splitting of a single exhaust source.

U.S. Pat. No. 2,558,023 to Walsh teaches a flared/conical exhaust outlet to direct heat and melt snow and ice. However, the flared/conical exhaust outlet of Walsh will cause an augmentation of sound rather than a diminution thereof. The flared end portion 14 of Walsh clearly indicates the primary heat disposal intent of the Walsh invention. It is also clear that the flared or fan-like termination for Walsh in a linear configuration (i.e. broom-like) is near optimal for melting snow and ice. Thus, structurally, the device of Walsh, by its flared end, allows heat transfer, but increases the acoustical energy emanating from Walsh's exhaust.

Therefore, it is readily apparent that there is a need for a device that reduces the sound level of an internal combustion engine via interaction with a travel surface.

BRIEF SUMMARY OF THE INVENTION

Briefly described, the present invention overcomes the above-mentioned disadvantages and meets the recognized need for such a device by providing a method and apparatus for reducing exhaust noise of internal combustion engines, wherein application of the present invention results in a substantial reduction in such noise, particularly as applied to four-stroke internal combustion engines.

According to its major aspects and broadly stated, the present invention in its preferred embodiment is a generally tubular exhaust extension configured and positioned in such a manner that the exhaust exits in close proximity to the ground, such as, for exemplary purposes only, within one-half inch from the ground travel surface. By orienting the extension in such a fashion, in lieu of relying on extension length alone, a measurable reduction in noise is achieved. That is, by utilizing the ground surface (i.e., grass or rough dirt) for absorption and dampening of sound waves, and by directing the exhaust tube directly downward into such a ground surface, a muffling effect is achieved. More specifically, the present invention is a muffling device comprising a section of tubing formed so as to enable exhaust expelled therefrom to be directed downward into the ground, or at an angle to the ground, and in close proximity thereto; thus, achieving substantial noise reduction compared to a vehicle lacking such a directed tube. Unlike the prior art, the straight end-attachment to the exhaust pipe of the present invention is the optimum configuration for maximum coupling of exhaust noise into the ground. The non-flared tubing of the present invention, when coupled to the ground surface, does not augment, and, in fact, reduces the acoustical energy emanating from the exhaust.

The present invention relates to a device that could be used by hunters and outdoorsmen to quieten the sound of their vehicles. More particularly, any internal combustion engine may have its exhaust noise substantially muffled through use of the present invention.

Accordingly, a feature and advantage of the present invention is its ability to provide a device that substantially reduces exhaust noise from internal combustion engines.

Another feature and advantage of the present invention is that manufacturers will have more design flexibility, allowing decibels to be reduced without applying restrictive devices on the engines.

Still another additional feature and advantage of the present invention is that manufacturers can use louder conventional mufflers and still reduce the overall sound with the present invention, thus increasing horsepower of the engine.

Yet another further feature and advantage of the present invention is that, when utilized in combination with an All Terrain Vehicle, it enables the user to observe wildlife at closer proximity than is normally possible without the device.

Still yet another feature and advantage of the present invention is its ability to provide for a quiet approach by a motor vehicle.

A further feature and advantage of the present invention is its ability to reduce engine noise output levels by approximately 50%.

Still a further feature and advantage of the present invention is that by reducing sound levels, it lessens or eliminates potential damage to the human ear.

Yet a further feature and advantage of the present invention is its ability to be utilized to quieten generators, such as those utilized in outdoor environments for backup household power or primary athletic field power.

These and other features and advantages of the present invention will become more apparent to one skilled in the art from the following description and claims when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, the present invention will be better understood by reading the Detailed Description of the Preferred and Alternate Embodiments with reference to the accompanying drawing figures, which are not necessarily drawn to scale, and in which like reference numerals denote similar structures and refer to like elements throughout, and in which:

FIG. 1 is a perspective view of a muffling device according to a preferred embodiment of the present invention shown mounted on an All Terrain Vehicle;

FIG. 2 is a side view of a muffling device according to a preferred embodiment of the present invention;

FIG. 3A depicts a perspective view of a muffling device according to an alternate embodiment of the present invention, shown mounted on an All Terrain Vehicle;

FIG. 3B is a side view of a muffling device according to the alternate embodiment of the present invention, shown in FIG. 3A; and

FIG. 4 is a side view of a muffling device according to an alternate embodiment of the present invention, shown mounted on an All Terrain Vehicle; and

FIG. 5 is side detail view of an alternate embodiment of the muffling device shown in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED AND SELECTED ALTERNATE EMBODIMENTS

In describing the preferred and alternate embodiments of the present invention, as illustrated in the Figures, specific terminology is employed for the sake of clarity. The invention, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish similar functions.

Referring now to FIGS. 1-2, muffling device 30 is preferably an elongated, generally cylindrically-shaped tube 22, formed from rubber, plastic, silicone rubber, metal, ceramic, or other suitable material. Tube 22 is of generally uniform diameter, but may comprise varying diameters. In the preferred embodiment, tube 22 comprises high temperature metal flex pipe extending from first end 25 through body 40 and terminating with high temperature silicone rubber at second end 50. Preferably tube 22 includes a fabric comprised of either synthetic or natural fiber woven and incorporated into the material forming tube 22. Tube 22 must be of sufficient rigidity to hold its shape and position, yet be resilient enough to give and return to its original position when struck by objects on the travel surface.

Preferably, muffling device 30 is installed on ATV 10 (as best shown in FIG. 1), wherein first end 25 of muffling device 30 is dimensioned to enable adaptation to any known tailpipe 20 of a vehicle muffler 20. Muffling device 30 is preferably configured with at least one bend 40 at a preferred approximate ninety-degree angle a suitable distance from the rear of the vehicle to allow clearance from the wheels and/or debris thrown up therefrom, and device 30 is directed towards the ground surface 60 as seen in FIG. 2. Second end 50 of muffling device 30 is disposed as close as possible to ground surface 60 without creating significant back pressure, and preferably less than one-half inch from ground surface 60, thereby causing a reduction in sound level.

It is noted that the quantity of sound reduction is a function of the character of the surface of the surrounding roadway, with grass surfaces providing the largest reduction, and rough dirt surfaces providing significant, but not as great as grass surface, reduction.

It is particularly noted that when operating a vehicle equipped with the present invention, wildlife can be approached at a closer range than when operating without the muffling device. Deer, typically startled and seen running from a distance of about 100 feet, may be more closely approached, for example even as close as 30 feet, before they begin to run.

In view of these observations of the unexpected benefits of the present invention, experiments were performed on the preferred embodiment using a decibel meter, the results of which are shown in TABLE 1. TABLE 1 EXPERIMENTAL RESULTS DECIBEL METER Slow speed conditions measured at distance of closest approach of 8 feet Stock muffler alone 82 dB Muffler adapted with present invention 76 dB Acceleration at full throttle from dead stop Stock muffler alone 92 dB Muffler adapted with present invention 88 dB Stopped, snap opening of throttle Stock muffler alone 89 dB Muffler adapted with present invention 86 dB Experimental conditions: 2001 POLARIS ™ SCRAMBLER ™ series ATV with 500 cc four-stroke engine, four-wheel drive. Open grass field. QUEST DIAGNOSTICS ® decibel meter. Distance from meter at time of measurement - approximately 8 feet.

It is particularly noted that 85 dB is considered to be the threshold of sound at which damage begins to occur to a human ear, wherein hearing loss occurs when subjected to sound of this level for extended periods of time. Thus the ability of the present invention to reduce sound near this level, or therebelow, advantageously lessens deterioration of hearing of individuals who are in close proximity to an internal combustion engine sound source equipped with the present invention.

In determining the quantity of reduction of sound by use of the present invention, it is instructive to calculate the reduction benefit derived from such use. Decibel levels are logarithmic ratios; that is, the ratio of the sound pressure is referenced to a standard sound pressure and the relative difference may be obtained. In the foregoing experimental results, and a noise reduction from 82 dB to 76 dB, the reduction ratio derivation is as follows: 20 log p ₁ /p _(0t)=82 dB 20 log p ₂ /p _(0t)=76 dB, where p_(0t) is the reference sound pressure, p₁ is the sound pressure under the test condition without the present invention and p₂ is the pressure recorded under the test condition using the present invention. Through calculation from the expressions above, a reduction in sound level of approximately 50% was obtained by use of the present invention at the experimental conditions reported hereinabove.

A second set of experiments were performed to determine the distance at which sound was no longer heard by a human observer from an operating ATV with and without a device of the present invention. For this test, the ATV was operated at a fixed speed around a central point, while the observer walked away from it. The test results are shown in TABLE 2. TABLE 2 EXPERIMENTAL RESULTS SUBJECTIVE AUDIBILITY TEST Audible distance test (point at which no further sound can be detected, while ATV was driven at constant speed around a fixed point) Stock muffler alone >730 feet Muffler adapted with present invention   312 feet Experimental conditions: 2001 POLARIS ™ SCRAMBLER ™ series ATV with 500 cc four-stroke engine, four-wheel drive. Open grass field.

Although sound was still heard with the stock muffler at a distance of 730 feet, due to lack of room to continue the distance test it was estimated from the above data that sound would disappear at approximately 830 feet.

FIG. 3A shows an alternate embodiment, wherein first end 25 of muffling device 30 extends aft from existing muffler tail pipe 20 of an All Terrain Vehicle, but then traverses in arcuate bend 40 downward, such that it bends at an angle less than ninety degrees. Muffling device 30 may practically comprise a bend 40 through an angle between thirty and less than ninety degrees. By then cutting second end 50 of muffling device 30, which is in proximity to, and approximately one-half inch from, ground surface 60, in a plane parallel to ground 60, as shown in FIG. 3B, an oval opening in second end 50 of muffling device 30 is formed. A support member 80 is mounted to frame 5 of ATV 10 providing support by attaching to muffling device 30 by use of a clamping means 90, and holds muffling device 30 at the correct angle. Support member 80 is secured to the frame 5 of ATV 10 via fastener 95, typically in the form of a threaded nut.

Tube 22 of the present invention may be of any suitable material that is resistant to high temperatures, such as those described above, and may also be reinforced utilizing a fabric of natural fibers or synthetic materials. In particular, high temperature silicone rubber hoses have been found most suitable. The material must be of sufficient rigidity to hold its form and position, yet flexible enough to give when obstructed by physical objects such as rocks in the travel path.

Referring now more specifically to FIGS. 4-5, illustrated therein are alternate embodiments of muffling device 30, wherein the alternate embodiment of FIG. 4 is substantially equivalent in form and function to that of the preferred embodiment detailed and illustrated in FIGS. 1-3B except as hereinafter specifically referenced. Specifically, the embodiment of FIG. 4 comprises muffling device 30, wherein muffling device 30 comprises tube 22 and spring 23, and wherein tube 22 has first end 25, bend 40, and second end 50. Tube 22 may selectively comprise a combination of tubing materials, such as high temperature metal flex pipe, extending from first end 25 through bend 40, and high temperature silicone rubber, extending from proximate bend 40 to second end 50. First end 25 of tube 22 is removably secured to tail pipe 20. Spring 23 is disposed within tube 22, wherein spring 23 comprises a formed sprung shape of a selected configuration. The configuration of spring 23 is such as to maintain second end 50 in a selected position proximate to ground surface 60, while permitting flexing of tube 22 during occasions when tube 22 strikes objects on ground surface 60.

Spring 23 may be a single sprung rod or alternately may be formed into a coiled configuration (as best shown in FIG. 5), wherein a coiled configuration of spring 23 could serve to provide support to tube 22. In the selected alternate embodiment of FIG. 5, spring 23 may be disposed within or without tube 22, wherein second end 50 is disposed normal to ground surface 60 and approximately one-half inch therefrom, but may alternately be disposed at an acute angle thereto.

In order to attach the tubing that comprises the muffling device 30 to the outlet pipe of the exhaust system of the internal combustion engine of an ATV, any suitable device, such as, for exemplary purposes only, a hose clamp, may be used.

In an alternate embodiment, it is envisioned that muffling device 30 may be bent through other angles.

It is further envisioned in an alternate embodiment that muffling device 30 may comprise more than one bend.

In addition, in an alternate embodiment, muffling device 30 may comprise bends within its interior while having a straight form to its exterior.

In an additional alternate embodiment, muffling device 30 may comprise a tube made from multiple components fitted together.

In still a further an alternate embodiment, muffling device 30 may be fabricated integrally to the exhaust outlet of the muffler of an internal combustion engine.

Having thus described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the within disclosures are exemplary only, and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention. Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Accordingly, the present invention is not limited to the specific embodiments illustrated herein, but is limited only by the following claims. 

1. A sound attenuating device for use with a muffler, said device comprising: a) at least one elongated tube comprising a first end, a second end, and at least one angle formed therebetween, and b) means for attaching said first end to the muffler, wherein said second end of said at least one elongated tube is proximate and open to a travel surface, and wherein said second end of said at least one elongated tube proximate the travel surface is adapted to attenuate exhaust sound from the muffler via interaction with the travel surface.
 2. The sound attenuating device of claim 1, wherein said at least one elongated tube is made from a material selected from the group consisting of metal, plastic, rubber, silicone rubber, ceramic, and combinations thereof.
 3. The sound attenuating device of claim 1, wherein said at least one elongated tube formed from a combination of high temperature flex pipe and high temperature silicone hose.
 4. The sound attenuating device of claim 2, wherein said selected material is silicone rubber.
 5. The sound attenuating device of claim 2, wherein said selected material is reinforced with fabric.
 6. The sound attenuating device of claim 5, wherein said fabric is comprised substantially of natural fiber.
 7. The sound attenuating device of claim 5, wherein said fabric is comprised substantially of synthetic fiber.
 8. The sound attenuating device of claim 1, wherein said at least one elongated tube has a substantially consistent diameter.
 9. The sound attenuating device of claim 8, wherein said first end of said at least one elongated tube is dimensioned to enable adaptation to the exhaust outlet of a vehicle.
 10. The sound attenuating device of claim 8, wherein said tube is bent downward in the direction of the travel surface at an angle approximately between thirty and ninety degrees from the direction of travel.
 11. The sound attenuating device of claim 10, wherein said second end is cut parallel to the surface of travel, and wherein said second end is oval-shaped.
 12. The sound attenuating device of claim 1, wherein said at least one elongated tube comprises a spring disposed internally to said at least one elongated tube, wherein said spring maintains flexibility of said second end of said at least one elongated tube, and wherein said spring maintains said second end selectively positioned proximate to the travel surface.
 13. The sound attenuating device of claim 12, wherein said spring is selected from the group consisting of spring rods, coil springs, and combinations thereof.
 14. The sound attenuating device of claim 1, wherein the exhaust sound is attenuated by approximately fifty percent.
 15. A method for muffling the sound from an internal combustion engine of a vehicle, said method comprising the steps of: a) taking a length of tubing, having a first end and a second end, wherein said second end is oval-shaped; b) providing attachment means for connecting said first end of said tubing to an exhaust outlet of the internal combustion engine; c) connecting said first end of said tubing to the exhaust outlet of the exhaust system of an internal combustion engine using said attachment means; d) adapting said second end of said tubing to attenuate engine sound via interaction with a travel surface; and e) directing said tubing in a direction toward the travel surface, such that said second end of said tubing is in proximity with the travel surface, whereby when the vehicle is set into motion and driven over the travel surface, the sound level of the internal combustion engine of the vehicle is substantially reduced.
 16. The method of claim 15, further comprising the step of: maintaining said length of tubing in a selected shape via a spring disposed therewithin.
 17. The method of claim 15, further comprising the step of: operating the all terrain vehicle over a roughly textured travel surface.
 18. The method of claim 15, further comprising the step of: operating the all terrain vehicle over a grass travel surface.
 19. The method of claim 15, further comprising the step of: operating the all terrain vehicle over a dirt travel surface.
 20. An apparatus for muffling the engine sound from the exhaust of an all terrain vehicle, said apparatus comprising a flexible tube comprising a bend, a first end and a second end, wherein said first end is attached to an outlet of the exhaust, and wherein said flexible tube is of sufficient length such that said second end of the tube is proximate to and directed at a travel surface, and wherein said second end is adapted to attenuate the engine sound from the exhaust via interaction with the travel surface. 